Author Topic: 6/1 silencing  (Read 4453 times)

veggie

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6/1 silencing
« on: September 01, 2020, 03:37:35 AM »
Thoughts ?
I currently have 2 large automotive mufflers in a long 25 ft exhaust system on my Roid. (20 ft of that is outdoors)
The pipe is 2" diameter all the way.
It discharges into my back yard area. Almost silent but not to my satisfaction.
I am considering adding a 3rd large muffler at the end of the run.
Would this be too much back pressure for a Lister type?

cheers
- 6/1 GM90 Listeroid - Delco 33si Alternator
- Changfa R175 - Lease/Neville Alternator
- Kubota Z482 - 4kw
- JiangDong R165 Air cooled - 2 kw

mikenash

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Re: 6/1 silencing
« Reply #1 on: September 01, 2020, 08:07:33 AM »
Veg have you seen the exhaust length/diameter chart in the CS installation manuals?  Someone will be able to reference it for you.  I suspect it might want to be fatter as it gets longer?

Also the various "buried" ones?  Effectively silent

Cheers

ajaffa1

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Re: 6/1 silencing
« Reply #2 on: September 01, 2020, 09:21:41 AM »
Hi Veggie, please see the text below cut and pasted from the listeroid 6/1 installation manual:

EXHAUST SYSTEM: A standard engine is fitted with an exhaust silencer. If the exhaust piping be extended to
the out side of the building up to a length of 3 meters, the exhaust silencer can be fitted on the end of iron
pipe screw 1 1/2 BSP.
If exhaust system is longer, following pipe size is recommended.
Pipe line: Up to 3 meter 38.0mm (1 , 4) Bore
3 to 6 meter 50.8 mm (2) bore
6 to 10 meters 63.5 mm (2) bore over
10 meters 76.Omm (3) bore
However, keep the exhaust system is as short as possible with a minimum number of bends and must be erected in
easily detachable sections to facilitate cleaning during overhaul. Never embed in concrete. A faulty system
can seriously reduce the power of the engine.

Bob

glort

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Re: 6/1 silencing
« Reply #3 on: September 01, 2020, 09:38:53 AM »

 Muffling is a fairly complex science but reducing gas speed as it exits to atmosphere and absorbing Pressure/ Sound waves are the main the keys. Positioning of the Muffler and or expansion chambers are Important.

I would first put an expansion chamber near the engine. That is just an empty vessel and I would make it around 10x the engine displacement.  This is to basically hold the majority of the exhaust pulse and allow it to bleed down out the pipe.
The old empty gas bottle would do well with this.

You can also cross the inlet and outlet pipes past one another so the inlet goes to the far end and the outlet is closest to the engine in offset positions.  The expansion chamber provided it is of sufficient size, would offset the back pressure of the long pipe  by letting the exhaust escape more gradually. The expansion  chamber is different to a muffler as it is hollow and performs a different function.

IMHO, this would be a better option than another muffler.  2 mufflers and 20 Ft of pipe is a fair bit of Muffling for that size engine and if that isn't enough, I think addressing gas speed rather than sound waves would  probably be better for performance and Silencing.
The other thing is looking at the back pressure nearest the engine. If it's over 7 Psi, I'd be looking at lowering it as that is detrimental to
power output and fuel consumption.  The lower the better and less pressure means less gas speed as well. You could test as the setup is now and after you install an expansion chamber.  The pressure will always be highest near the engine as pushing gas or water down a pipe creates a boundary layer due to friction on the pipe. Bends increase back pressure as they reduce the inertia of the gas and create more friction. The pressure will also reduce further along as the gas cools and contracts but it's the pressure at the port one has to be wary of.

Another way of reducing gas speed and increasing sound suppression would be to split the pipe and run another one with the mufflers in parallel rather than in series.  If practical, you could cut the pipe you have in half, put in a Y section with a Muffler on each end.
I'd still use the offset expansion chamber so the pressure waves are dispersed and reflected rather than having a Straight shot along the pipe. 

The other thing is where the  Pipe is exiting?  If it's near an area you frequent, can you move it to an area further away from where you might normally be and hear it? Putting it up Higher and out of line of sight may help or rather than a full on earth muffler, just sink the end of the pipe in a drum of large gravel or stones.

The other thing is, is it definitely the exhaust you are hearing and not the intake?
In my experience, most diesels that come with a muffler do not make the main racket through the muffler, they make it through the intake.  The China Diesels, The ruggerini's  and lombardinis and particularly the Kubotas are noisy as all get out on the INTAKE.
It's easy to test, I wrap a towel around the air cleaner and if the sound goes down, which it always does, then you know where the sound is coming from.

I have had an ancient single Lung air compressor for... well all my adult life actually.  The air cleaner recently fell apart.  Needing to use the thing and not wanting to get crap in the old antique,  I got a piece of pipe, welded the correct  nipple  on the end of the oversize end plate of the pipe and then packed it with some filter material I had.
The thing has gone from being able to hear it wherever I was on the property including in the house,  to being so quiet  the only thing you can hear is the electric motor running.  What an eye opener.   This temporary solution is going to be  very permanent.

Haven't see or heard your setup but determining where the noise is coming from may be worth while.
Other than that, I'd suggest looking at the expansion chamber and position of the outlet before yet another muffler.

ajaffa1

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Re: 6/1 silencing
« Reply #4 on: September 01, 2020, 01:38:01 PM »
Hi Veggie, when I installed my ST2 startomatic the exhaust noise was way too much for my Wife. So I went and bought a dustbin, I dug a hole and dropped the bin into it. I connected the exhaust pipe into the top of the bin and fitted another flexible pipe to the bottom of the bin. I dug a trench about 20 feet long for the bottom pipe to sit in. I then surrounded the whole thing in concrete and put the top soil back over it all.

The exhaust is now silent, more than can be said for my Wife.

Bob

veggie

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Re: 6/1 silencing
« Reply #5 on: September 02, 2020, 05:52:49 PM »
Another way of reducing gas speed and increasing sound suppression would be to split the pipe and run another one with the mufflers in parallel rather than in series.  If practical, you could cut the pipe you have in half, put in a Y section with a Muffler on each end.

That's a good idea.!
I will look into doing that.

The system is very quite as-is, but neighbors and wife can still here a puff...puff...puff.
I don't mind it of course, but non-lister humans don't necessarily like it.

Digging a hole in my back garden is not an option at this time.
- 6/1 GM90 Listeroid - Delco 33si Alternator
- Changfa R175 - Lease/Neville Alternator
- Kubota Z482 - 4kw
- JiangDong R165 Air cooled - 2 kw

veggie

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Re: 6/1 silencing
« Reply #6 on: September 04, 2020, 03:38:24 PM »
Report

Ok ... I tried a third muffler but it hardly made any difference.
The whoosh ... whoosh ... whoosh noise is still prevelent due to the restriction in the mufflers and I don't think the added back pressure is good for the system.

The next thing I am trying is a large pressure dissipation chamber much like some others have done underground but mine will be above ground.
The plan is to use a steel garbage can lined with Roxul fireproof sound insulation. This will allow the exhaust pulse cool to dissipate before leaving the can with much less force.

Design issue !
The muffler is outdoor.
One concern I have is condensation and freezing. Here in the frozen north it is very likely that the engine will be running when the outside temperatures are -15C.
Does anyone know a 'rule of thumb' for how much exhaust water is generated per liter of fuel?
I can put a layer of sand/gravel in the bottom of the chamber and drill drain holes.

cheers
veggie


- 6/1 GM90 Listeroid - Delco 33si Alternator
- Changfa R175 - Lease/Neville Alternator
- Kubota Z482 - 4kw
- JiangDong R165 Air cooled - 2 kw

glort

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Re: 6/1 silencing
« Reply #7 on: September 05, 2020, 11:40:12 AM »

I believe the 3rd muffler did nothing because this is a pressure issue.  You mentioned the Puff puff and that's pressure.
That's why I suggested the dual system and the resonator,  to reduce the pressure and gas speed.

I would suggest the condensation is dependent on Humidity in the air, not in the fuel.
If you are going to keep the present mufflers, I would suggest locating them close to the engine so they get hot and dry out. Rear Mufflers are known to rust out before front mufflers and resonators on cars because they get hotter and have less condensation.

Anything you put on the end of the exhaust would be increasing back pressure. I'd be trying to reduce that for engine performance and economy.

veggie

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Re: 6/1 silencing
« Reply #8 on: September 11, 2020, 04:48:51 PM »
Hi Veggie, please see the text below cut and pasted from the listeroid 6/1 installation manual:

EXHAUST SYSTEM: A standard engine is fitted with an exhaust silencer. If the exhaust piping be extended to
the out side of the building up to a length of 3 meters, the exhaust silencer can be fitted on the end of iron
pipe screw 1 1/2 BSP.
If exhaust system is longer, following pipe size is recommended.
Pipe line: Up to 3 meter 38.0mm (1 , 4) Bore
3 to 6 meter 50.8 mm (2) bore
6 to 10 meters 63.5 mm (2) bore over
10 meters 76.Omm (3) bore
However, keep the exhaust system is as short as possible with a minimum number of bends and must be erected in
easily detachable sections to facilitate cleaning during overhaul. Never embed in concrete. A faulty system
can seriously reduce the power of the engine.

Bob

That's interesting.
Both mikenash and your data do in fact state that the pipe diameter should increase as the run gets longer.
My thinking was that as the outdoor run gets longer the gas would get cooler and contract along the way which would negate the need for larger diameters. I currently use 2" pipe.

I am leaning towards the Garbage Can method suggested by ajaffa1.
Here's an example from our member rbodell... and his is only half buried.
https://www.youtube.com/watch?v=v1ZJ8e3ihZg

... I am also considering this one. It's interesting if you look at what happens when he added the top 2 tires.
They start bouncing slightly. Absorbing the exhaust pulse and taking away the energy.
https://www.youtube.com/watch?v=XZBL5R47E84

- 6/1 GM90 Listeroid - Delco 33si Alternator
- Changfa R175 - Lease/Neville Alternator
- Kubota Z482 - 4kw
- JiangDong R165 Air cooled - 2 kw

glort

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Re: 6/1 silencing
« Reply #9 on: September 11, 2020, 08:03:44 PM »

With the tyres the guy has made a resonator. An empty chamber that absorbs the pulses of gas and bleeds them out slowly through the small hole in the grinding disk he has in the centre of the tyre.  The tyre on top acts like a Muffler further  reducing the gas speed and pressure.